Lots of good products mentioned here and all are worthy.
I find that different materials make a difference, as does the quality of material. You'll usually find me at the $1/$2 bins at Wal-Mart, where the composition of the fabric is up for grabs. (The bolt's label often is not what is on the bolt.) Try as I might to come home with 100% cotton, sure as shootin' there'll be a poly/cotton blend in the bunch. I will use it because my "discretionary income" is gone and the nearest fabric store is 20 miles away.
Back to the point. Crayola Washable Markers for kids have washed out of everything, even after being lightly pressed. When the quilt is finished, and before it is washed, it looks like a mess but the marks have always washed out no matter what the composition of the yardage.
The only shortcoming with Crayola Washable Markers is inability to mark dark fabrics. Here I use a white marking pencil.